U.S. patent number 6,589,445 [Application Number 09/887,335] was granted by the patent office on 2003-07-08 for light-reaction type optically active compound, light-reaction type chiral agent, liquid crystal composition, liquid crystal color filter, optical film, recording medium, and method of changing twist structure of liquid crystal.
This patent grant is currently assigned to Fuji Photo Film Co., Ltd.. Invention is credited to Keiichiro Hayashi, Mitsuyoshi Ichihashi, Takekatsu Sugiyama.
United States Patent |
6,589,445 |
Sugiyama , et al. |
July 8, 2003 |
LIGHT-REACTION TYPE OPTICALLY ACTIVE COMPOUND, LIGHT-REACTION TYPE
CHIRAL AGENT, LIQUID CRYSTAL COMPOSITION, LIQUID CRYSTAL COLOR
FILTER, OPTICAL FILM, RECORDING MEDIUM, AND METHOD OF CHANGING
TWIST STRUCTURE OF LIQUID CRYSTAL
Abstract
A light-reaction type optically active compound and
light-reaction type chiral agent of the following general formula
(I) or (II). In the general formulae, R.sup.1 and R.sup.2 represent
a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, an
acryloyloxyalkyloxy group having 3 to 15 carbon atoms in total or a
methacryloyloxyalkyloxy group having 4 to 15 carbon atoms in total.
##STR1## ##STR2##
Inventors: |
Sugiyama; Takekatsu
(Shizuoka-ken, JP), Ichihashi; Mitsuyoshi
(Shizuoka-ken, JP), Hayashi; Keiichiro (Shizuoka-ken,
JP) |
Assignee: |
Fuji Photo Film Co., Ltd.
(Kanagawa, JP)
|
Family
ID: |
27481388 |
Appl.
No.: |
09/887,335 |
Filed: |
June 25, 2001 |
Foreign Application Priority Data
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Jun 27, 2000 [JP] |
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2000-193142 |
Jun 27, 2000 [JP] |
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2000-193143 |
Jan 12, 2001 [JP] |
|
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2001-5740 |
Jan 12, 2001 [JP] |
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2001-5741 |
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Current U.S.
Class: |
252/299.01;
252/299.61; 430/7; 430/19; 252/299.62; 349/106; 349/2; 428/1.1;
252/299.7 |
Current CPC
Class: |
C09K
19/586 (20130101); C07D 493/04 (20130101); G03C
1/73 (20130101); C09K 2323/00 (20200801); Y10T
428/10 (20150115) |
Current International
Class: |
C07D
493/00 (20060101); C07D 493/04 (20060101); C09K
19/58 (20060101); G03C 1/73 (20060101); C09K
019/52 (); C09K 019/34 (); C09K 019/32 (); C09K
019/38 (); G02F 001/13 () |
Field of
Search: |
;252/299.61,299.62,299.01,1.1 ;428/1.1 ;430/20,7 ;349/106,2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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11-248943 |
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Sep 1999 |
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JP |
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2000-44451 |
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Feb 2000 |
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JP |
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9-506088 |
|
Jun 2000 |
|
JP |
|
WO 95/16007 |
|
Jun 1995 |
|
WO |
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WO 00/34808 |
|
Jun 2000 |
|
WO |
|
Other References
Primary Examiner: Wu; Shean C.
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A light-reaction type optically active compound represented by
the following general formula (I): ##STR45##
in which formula, R.sup.1 represents a hydrogen atom, an alkoxy
group having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group
having 3 to 15 carbon atoms in total, or a methacryloyloxyalkyloxy
group having 4 to 15 carbon atoms in total.
2. The light-reaction type optically active compound according to
claim 1, wherein in the general formula (I), R.sup.1 is an
acryloyloxyalkyloxy group having 3 to 15 carbon atoms in total or a
methacryloyloxyalkyloxy group having 4 to 15 carbon atoms in
total.
3. The light-reaction type optically active compound according to
claim 1, wherein in the general formula (I), R.sup.1 is a hydrogen
atom or an alkoxy group having 1 to 15 carbon atoms.
4. A light-reaction type chiral agent for changing twisting power
of a liquid crystal when irradiated by light, the agent comprising
a compound represented by general formula (I) as follows:
##STR46##
in which formula R.sup.1 represents a hydrogen atom, an alkoxy
group having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group
having 3 to 15 carbon atoms in total, or a methacryloyloxyalkyloxy
group having 4 to 15 carbon atoms in total.
5. A liquid crystal composition comprising the light-reaction type
optically active compound according to claim 1.
6. A liquid crystal color filter comprising the light-reaction type
optically active compound according to claim 1.
7. An optical film comprising the light-reaction type optically
active compound according to claim 1.
8. A recording medium comprising the light-reaction type optically
active compound according to claim 1.
9. A method for changing twist structure of liquid crystals, the
method comprising the steps of: providing the liquid crystal
composition according to claim 5; and irradiating the liquid
crystal composition with light to cause a change of twisting power
of the liquid crystals.
10. A light-reaction type chiral agent for changing twisting power
of a liquid crystal when irradiated by light, the agent comprising
a compound represented by general formula (II) as follows:
##STR47##
in which formula R.sup.2 represents an acryloyloxyalkyloxy group
having 3 to 15 carbon atoms in total, or a methacryloyloxyalkyloxy
group having 4 to 15 carbon atoms in total.
11. The light-reaction type chiral agent according to claim 10,
wherein in the general formula (II), R.sup.2 is a hydrogen atom or
an alkoxy group having 1 to 15 carbon atoms.
12. A liquid crystal composition comprising the light-reaction type
chiral agent according to claim 10.
13. A method for changing twist structure of liquid crystals, the
method comprising the steps of: providing the liquid crystal
composition according to claim 12; and irradiating the liquid
crystal composition with light to cause a change of twisting power
of the liquid crystals.
14. A liquid crystal color filter comprising the light-reaction
type chiral agent of claim 10.
15. An optical film comprising the light-reaction type chiral agent
according to claim 10.
16. A recording medium comprising the light-reaction type chiral
agent according to claim 10.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel light-reaction type
optically active compound, a light-reaction type chiral agent which
changes the helical structure of a liquid crystal, a liquid crystal
composition, an optical film, a liquid crystal color filter, a
recording medium, and a method of changing the twist structure of
helices of liquid crystals.
2. Description of the Related Art
Recently, liquid crystal materials such as cholesteric liquid
crystals and the like having a helical structure and showing
various selective reflected colors by twisting power (twist angle)
of the helix have become prominent. Further, due to excellent
selective reflecting property and excellent color purity of
selective reflected light, the materials have become widely used in
optical films, liquid crystal color filters, recording media and
the like.
For example, a color filter used in a color liquid crystal display
or the like is generally constituted of picture elements of red
(R), green (G) and blue (B), and black matrices formed for the
purpose of improving display contrast in gaps between the elements.
Main types of such a color filter are conventionally those obtained
by dispersing a pigment in a resin, or dyeing a resin with a dye.
As a production method thereof, methods are usual in which a
coloring resin solution is applied on a glass substrate by spin
coating or the like to form a coloring resist layer, and patterning
by a photolithography method is conducted to form color filter
picture elements, or coloring picture elements are directly printed
on a substrate.
However, for example, a production method by printing has problems
in that resolution of picture elements is low and formation of an
image pattern of high accuracy is difficult, and a production
method by spin coating has problems in that material loss is large
and application unevenness when applying on a substrate having
large area is significant. Further, in a production method by
electrodeposition, a color filter having relatively high resolution
and having small unevenness of a colored layer can be obtained, but
the production process is complicated and management of liquids is
difficult.
As described above, there is a great desire for a method which can
produce a color filter having high quality at high efficiency with
small material loss and in a simple manner.
On the other hand, as characteristics of a color filter,
high-percentage transmission and color purity are required.
Recently, improvements corresponding to the above-mentioned
requirements have been attempted by optimizing a dyeing resin and
kind of dye in a method using a dye, and by using a more finely
dispersed pigment in a method using a pigment. However, in recent
liquid crystal display (LCD) panels, requirements for the percent
transmission and color purity of a color filter are extremely high.
Particularly in a color filter for a reflection type LCD,
compatibility between white display of paper white, contrast and
color reproducibility is difficult, while color filters produced by
dyeing a resin with a dye or dispersing a pigment in a resin
according to conventional production methods are all color filters
of light absorption type. Therefore, improvement of color purity by
a further increase in percent transmission is almost at an upper
limit.
Against the above-mentioned situations, a color filter utilizing
polarization, having a cholesteric liquid crystal as a main
component, is known. This color filter utilizing polarization shows
high efficiency of utilizing light and has more remarkable
abilities also in percent transmission and color purity than a
color filter of light absorption type, since a certain light amount
is reflected and other light is transmitted to display images in
the color filter utilizing polarization. On the other hand, as a
method of producing the same filter, a method in which a film is
formed on a substrate using a spin coat method or the like is
usually conducted from the standpoint of uniform thickness.
However, this method has a problem of large material loss and is
disadvantageous in the point of cost.
As a means which can solve the above-mentioned problems, can secure
uniformity of color purity and the like of a color filter film, and
can also realize a reduction in the number of production steps, a
method using a light-reaction type chiral compound is useful. This
method uses the theory that when a liquid crystal composition
containing a light-reaction type chiral compound is irradiated
pattern-wise with light having a reaction wavelength of this chiral
compound, the reaction of the chiral compound progresses depending
on the strength of the irradiation energy, and helical pitch (twist
angle of helix) of the liquid crystal compound changes.
Consequently, a selective reflection color is formed for each
picture element simply by pattern exposure including a difference
between light amounts. Namely, there is a merit that patterning for
forming a color filter can be completed by one-time mask exposure
using a mask having different transmission light amounts.
Therefore, a film functioning as a color filter can be formed by
effecting patterning by image-wise light irradiation, and then
solidifying the patterned cholesteric liquid crystal compound. This
can be applied also to films for optical use or recording of
images, and the like.
Particularly when a color filter is produced by one-time mask
exposure or the like, it is desired that three primary colors, B
(blue), G (green) and R (red), can be formed with high color purity
by one-time exposure. However, when a rate of change of twist of a
liquid crystal is low, sufficient color purity is not obtained.
Therefore, in view of displaying three primary colors having high
color purity by one-time exposure, it is necessary to use a chiral
compound (chiral agent) that is capable of changing twisting power
of a helical structure of a liquid crystal compound and that has a
high rate of change of twist as a light-reaction type chiral
compound. Namely, a range of selectively reflected hues is enlarged
due to change of light amount by using a chiral compound having a
high rate of change of twist.
Further, Japanese Patent Application Laid-Open (JP-A) No. 11-248943
discloses use of a polymerizable mesogene compound having an
isosorbide skeleton in a chiral mother nucleus as a chiral compound
constituting a polarization plate of reflection type in a wide
range. This polymerizable mesogene compound can act on a liquid
crystal compound to cause change of the helical structure of the
liquid crystal. However, when a reflection wavelength range of a
polarization plate described in the above-mentioned publication is
changed, namely, the helical structure (twisting power of helix) of
a liquid crystal is changed so as to show the desired selective
reflection, control of the change is carried out by a mixing ratio
(of amounts used) of the mesogene compound to a non-chiral compound
(liquid crystal), and light and light amount thereof are not
correlated at all. That is, in this publication, there is utterly
no suggestion that the helical structure (twisting power of helix)
of a liquid crystal is changed by changing light amount, and there
is also no suggestion that compounds exemplified in the publication
are useful in the point of rate of change of twisting power in
response to light.
As described above, a light-reaction type chiral agent as follows
has not been proposed until now. This agent has light reactivity
which can change orientation structures such as the helical pitch
of a liquid crystal (twisting power, twist angle of helix) and the
like by controlling light amounts used in irradiation. Further, in
the case of a cholesteric liquid crystal phase containing a nematic
liquid crystal compound, for example, the agent is able to provide
significant changes of the helical pitch (twisting power), such as
a wide range of selectively reflectable wavelengths, various
selective reflections and, particularly, display of three primary
colors (R, G, B) at high color purity, and the like.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned
various conventional problems and to attain the following
objects.
Namely, a first object of the present invention is to provide a
light-reaction type optically active compound which has light
sensitivity and can be isomerized by light to reveal significant
structural change. A second object of the present invention is to
provide a light-reaction type chiral agent which can control the
orientation of a liquid crystalline compound and manifests high
rate of change of twisting power (twist angle, helical pitch) of a
liquid crystal (hereinafter, sometimes referred to as twisting
change rate) due to light, and in the case, for example, of a
cholesteric liquid crystal phase, which can give selective
reflection in a wide range containing three primary colors (B, G,
R) and can display the three primary colors with high color
purities.
A third object of the present invention is to provide a liquid
crystal composition which contains a light-reaction type optically
active compound or light-reaction type chiral agent that can change
twisting power of a liquid crystal by light, and that has high
twisting change rate, and which can change optical properties by
sterically significantly controlling the orientation condition of a
liquid crystal molecule by light, and in the case of, for example,
a cholesteric liquid crystal, which shows selective reflection
colors in a wide range containing three primary colors due to
irradiation with light, and further, can display the three primary
colors with excellent color purity.
Further, a fourth object of the present invention is to provide a
liquid crystal color filter which contains a light-reaction type
optically active compound or light-reaction type chiral agent that
can significantly change twisting power of a liquid crystal when
irradiated with light and has high color purity. A fifth object of
the present invention is to provide an optical film which contains
a light-reaction type optically active compound or light-reaction
type chiral agent that can significantly change twisting power of a
liquid crystal by irradiation with light, and in the case of, for
example, a cholesteric liquid crystal phase, which manifests a
wider selective reflection range and has high color purity. A sixth
object of the present invention is to provide a recording medium
which contains a light-reaction type optically active compound or
light-reaction type chiral agent that can significantly change
twisting power of a liquid crystal when irradiated with light, and
that can form a bright image by image-wisely changing light
amounts, and when, for example, the liquid crystal phase is a
cholesteric liquid crystal phase, which can form images composed of
selective reflection colors manifesting a wide hue range and having
high color purity.
Further, a seventh object of the present invention is to provide a
method of changing twist structure of a liquid crystal in which the
twisting power (twist angle) of a liquid crystal can be changed
significantly by irradiating with light a liquid crystal
composition containing a light-reaction type optically active
compound or light-reaction type chiral agent that reveals high
twisting change rate.
A first aspect of the present invention is a light-reaction type
optically active compound of the following general formula (I):
##STR3##
In the formula, R.sup.1 represents a hydrogen atom, an alkoxy group
having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having 3
to 15 carbon atoms in total or a methacryloyloxyalkyloxy group
having 4 to 15 carbon atoms in total.
A second aspect of the present invention is a light-reaction type
chiral agent which is composed of a compound of the general formula
(I) or (II), and changes the twisting power of a liquid crystal by
irradiation with light. ##STR4## ##STR5##
wherein, R.sup.1 and R.sup.2 represent a hydrogen atom, an alkoxy
group having 1 to 15 carbon atoms, anacryloyloxyalkyloxy group
having 3 to 15 carbon atoms in total or a methacryloyloxyalkyloxy
group having 4 to 15 carbon atoms in total.
A third aspect of the present invention is a liquid crystal
composition containing the above-mentioned light-reaction type
optically active compound.
A fourth aspect of the present invention is a liquid crystal
composition containing the above-mentioned light-reaction type
chiral agent.
A fifth aspect of the present invention is a liquid crystal color
filter containing the above-mentioned light-reaction type optically
active compound.
A sixth aspect of the present invention is an optical film
containing the above-mentioned light-reaction type optically active
compound.
A seventh aspect of the present invention is a recording medium
containing the above-mentioned light-reaction type optically active
compound.
An eighth aspect of the present invention is a method of changing
the twist structure of a liquid crystal including a step of
irradiating the above-mentioned liquid crystal composition with
light to cause a change of the twisting power of the liquid
crystal.
A ninth aspect of the present invention is a liquid crystal color
filter containing the above-mentioned light-reaction type chiral
agent.
A tenth aspect of the present invention is an optical film
containing the above-mentioned light-reaction type chiral
agent.
An eleventh aspect of the present invention is a recording medium
containing the above-mentioned light-reaction type chiral
agent.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1A is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1B is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1C is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1D is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1E is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1F is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1G is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1H is a sectional view showing a process of producing a liquid
color filter of the present invention.
FIG. 1I is a sectional view showing a process of producing a liquid
color filter of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be illustrated successively.
<Light-reaction Type Optically Active Compound>
The light-reaction type optically active compound of the present
invention is a left-twisting compound of the following general
formula (I). ##STR6##
In the formula, R.sup.1 represents a hydrogen atom, an alkoxy group
having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having 3
to 15 carbon atoms in total or a methacryloyloxyalkyloxy group
having 4 to 15 carbon atoms in total.
Examples of the above-mentioned alkoxy group having 1 to 15 carbon
atoms include a methoxy group, ethoxy group, propoxy group, butoxy
group, hexyloxy group, octyloxy group, dodecyloxy group and the
like, and, of these, alkoxy groups having 1 to 10 carbon atoms are
preferable, and alkoxy groups having 1 to 8 carbon atoms are
particularly preferable.
Examples of the above-mentioned acryloyloxyalkyloxy group having 3
to 15 carbon atoms in total include an acryloyloxy group,
acryloyloxyethyloxy group, acryloyloxypropyloxy group,
acryloyloxyhexyloxy group, acryloyloxybutyloxy group,
acryloyloxydecyloxy group and the like, and, of these,
acryloyloxyalkyloxy groups having 3 to 13 carbon atoms are
preferable, and acryloyloxyalkyloxy groups having 3 to 11 carbon
atoms are particularly preferable.
Examples of the above-mentioned methacryloyloxyalkyloxy group
having 4 to 15 carbon atoms in total include a methacryloyloxy
group, methacryloyloxyethyloxy group, methacryloyloxyhexyloxy group
and the like, and, of these, methacryloyloxyalkyloxy groups having
4 to 14 carbon atoms are preferable, and methacryloyloxyalkyloxy
groups having 4 to 12 carbon atoms are particularly preferable.
The molecular weight of a light-reaction type optically active
compound of the above-mentioned general formula (I) is preferably
300 or more. Those showing high solubility with liquid crystalline
compounds described below are preferable, and those having a
solubility parameter SP value near those of the liquid crystalline
compounds are more preferable.
Specific examples of a light-reaction type optically active
compound of the above-mentioned general formula (I) include, but in
the present invention are not limited to, the following compounds
(exemplified compounds (1) to (12)). ##STR7## ##STR8##
Next, examples of synthesizing light-reaction type optically active
compounds of the present invention (compounds of the general
formula (I)) will be described. A number in parentheses after a
light-reaction type optically active ok compound represents the
number of one of the above-exemplified light-reaction type
optically active compounds (exemplified compounds).
[Synthesis of Light-reaction Type Optically Active Compound
(2)]
4-methoxycinnamic acid (4 g, 0.022 mole) and dimethylformamide (2
to 3 drops) were dissolved in tetrahydrofuran (50 mL), and to this
was further added dropwise a solution prepared by dissolving oxalyl
chloride (10 mL, 0.034 mole) in tetrahydrofuran (20 mL), and these
were reacted for 2 hours. The solvent and excess oxalyl chloride in
the reaction solution were distilled off under reduced pressure.
Then, the solution was diluted with tetrahydrofuran (30 mL), and to
this was added isomannide (1.3 g, 0.009 mol). To this was further
added dropwise triethylamine (18.6 mL, 0.13 mole) dissolved in
tetrahydrofuran (20 mL) while stirring, and the mixture was stirred
for 3 hours. Then, to the reaction solution was added 10%
hydrochloric acid (50 mL) and ethyl acetate (100 mL) and this
mixture was stirred, and separated. A resulting organic layer was
washed once with saturated saline solution (50 mL), twice with
saturated sodium bicarbonate solution (50 mL) and twice with
saturated saline solution (50 mL) in this order, and dried over
magnesium sulfate. Further, the organic solvent was distilled off
under reduced pressure. Then, the solution was purified by silica
gel column chromatography, using as a developing solvent a mixed
solution of n-hexane-ethyl acetate (2:3 v/v), and re-crystallized
(methanol-ethyl acetate) to obtain a pale yellow powdery crystal
(4.1 g, 38%).
Identification results (data) of the pale yellow powdery crystal as
obtained above are shown below.
Melting point Tm=132.5.degree. C., [.alpha.].sub.D.sup.25
407.degree. (c0.10, EtOAc).
.sup.1 H-NMR (CDCl.sub.3): .delta. (in ppm from tetramethylsilane)
7.70 (2H, d), 7.50 (4H, d), 6.90 (4H, d), 6.40 (2H, d), 5.30-5.20
(2H, m), 4.85-4.80 (2H, m), 4.15-3.90 (4H, m), 3.45 (6H, s).
[Synthesis of Light-reaction Type Optically Active Compound
(7)]
Trans-4-courmaric acid (15 g, 0.091 mole) and potassium carbonate
(30 g, 0.22 mole) were added todimethylformamide (100 mL), and to
this mixture was added dropwise 1-iododecane (54 g, 0.21 mole)
while heating in an oil bath. After stirring for 6 hours, insoluble
components were filtrated off. The remaining solution was diluted
with ethyl acetate (400 mL) and washed with saturated saline
solution (200 mL). Further, the organic solvent was distilled off
under reduced pressure. Then, to the remaining solution was added a
solution prepared by dissolving ethanol (100 mL) and potassium
hydroxide (10 g, 0,18 mole) in water (50 mL), and this mixture was
refluxed for 1 hour. The reaction solution was poured into diluted
hydrochloric acid, and deposited crystal was filtrated off before
being dried to obtain 4-n-decyloxycinnamic acid (14.6 g, 53%) in
the form of a colorless crystalline powder.
The resulting 4-n-decyloxycinnamic acid (3 g, 0.010 mole) and
dimethylformamide (2 to 3 drops) were dissolved in tetrahydrofuran
(50 mL). To this mixture was further added dropwise a solution
prepared by dissolving oxalyl chloride (1.26 mL, 0.015 mole) in
tetrahydrofuran (20 mL), and these were reacted for 2 hours. The
solvent and excess oxalyl chloride in the reaction solution were
distilled off under reduced pressure. Then, the solution was
diluted with tetrahydrofuran (50 mL), and to this was added
isomannide (0.6 g, 0.004 mol). To this was further added dropwise
triethylamine (8.2 mL, 0.06 mole) dissolved in tetrahydrofuran (20
mL) while stirring, and this mixture was stirred for 3 hours. Then,
to the reaction solution was added 10% hydrochloric acid (50 mL)
and ethyl acetate (100 mL), and this mixture was stirred, and
separated. A resulting organic layer was washed once with saturated
saline solution (50 mL), twice with saturated sodium bicarbonate
solution (50 mL) and twice with saturated saline solution (50 mL)
in this order, and dried over magnesium sulfate. Further, the
organic solvent was distilled off under reduced pressure, and then
re-crystallized (n-hexane-ethyl acetate) to obtain a colorless
powdery crystal (0.45 g, 16%).
Identification results (data) of the colorless crystalline powder
as obtained above are shown below.
Melting point Tm=72.4.degree. C., [.alpha.].sub.D.sup.25
280.degree. (c0.11, EtOAc).
.sup.1 H-NMR (CDCl.sub.3): .delta. (in ppm from tetramethylsilane)
7.72 (2H, d), 7.48 (4H, d), 6.90 (4H, d), 6.38 (2H, d), 5.30-5.20
(2H, m), 4.85-4.78 (2H, m), 4.15-3.90 (8H, m), 1.90-1.30 (32H, m),
0.9 (6H, t).
<Light-reaction Type Chiral Agent>
The light-reaction type chiral agent is composed of a compound
(light-reaction type optically active compound) of the general
formula (I) or a compound of the general formula (II), and changes
the twisting power of a crystal when irradiated with light.
A light-reaction type optically active compound of the
above-mentioned general formula (I) has features that it functions,
when used together with a crystalline compound, as a chiral
compound (light-reaction type chiral agent) which changes the
helical structure of the crystalline compound, and, when irradiated
with light having a certain wavelength, the light-reaction type
optically active compound having a sensitive wavelength at that
wavelength range is sensitized, and this compound controls the
orientation structure of the crystalline compound, and can
simultaneously cause a change of the helical pitch of a crystal,
namely, the twisting power of the helical structure (HTP: helical
twisting power).
A light-reaction type chiral agent composed of a compound of the
following general formula (II) also has features that it can
control orientation structure of a crystalline compound and can
cause change of the helical pitch, HTP, of the crystal when
irradiated with light. That is, these light-reaction type chiral
agents are compounds which cause, when irradiated with light
(ultraviolet to visual to infrared), a change of the twisting power
of a helical structure derived from a crystalline compound,
preferably a nematic crystalline compound, and has a chiral site
and a site causing a structural change by irradiation with light,
as necessary sites (molecule structural units), in the same
molecule.
Additionally, a light-reaction type chiral agent of the following
general formula (I) or (II) can significantly change HTP of,
particularly, a liquid crystal molecule. Consequently, for example,
in the case of a cholesteric liquid crystal (liquid crystal phase)
using a nematic liquid crystal compound as a crystalline compound,
selective reflectances ranging over a wider wavelength range
including three primary colors, B (blue), G (green) and R (red),
can be obtained. The selective reflection property of light
wavelength is determined by the twist angle of the helical
structure of the liquid crystal molecule. When this angles varies
more significantly, the width of colors selectively reflectable
becomes wider, giving usefulness.
The above-described HTP represents the twisting power of the
helical structure of a liquid crystal, namely,
1/(pitch.times.concentration of chiral agent [weight fraction])=HTP
[.mu.m.sup.-1 ], and, for example, can be obtained by measuring the
helical pitch (one cycle of helical structure; .mu.m) of a liquid
crystal molecule at a certain temperature, and converting this
value using the concentration of the chiral agent.
When a selective reflection color is formed by the illuminance of
light using the light-reaction type chiral agent, the
above-mentioned change rate of HTP (=HTP before irradiation/HTP
after irradiation) is preferably 1.5 or more, further preferably
2.5 or more if HTP becomes smaller after irradiation, and
preferably 0.7 or less, further preferably 0.4 or less if HTP
becomes larger after irradiation.
Next, compounds of the general formula (II) will be described.
##STR9##
In the formula, R.sup.2 represents a hydrogen atom, an alkoxy group
having 1 to 15 carbon atoms, an acryloyloxyalkyloxy group having 3
to 15 carbon atoms in total or a methacryloyloxyalkyloxy group
having 4 to 15 carbon atoms in total.
Examples of the above-mentioned alkoxy group having 1 to 15 carbon
atoms include a methoxy group, ethoxy group, propoxy group, butoxy
group, hexyloxy group, dodecyloxy group and the like, and, of
these, alkoxy groups having 1 to 12 carbon atoms are preferable,
and alkoxy groups having 1 to 8 carbon atoms are particularly
preferable.
Examples of the above-mentioned acryloyloxyalkyloxy group having 3
to 15 carbon atoms in total include an acryloyloxyethyloxy group,
acryloyloxybutyloxy group, acryloyloxydecyloxy group and the like,
and, of these, acryloyloxyalkyloxy groups having 5 to 13 carbon
atoms are preferable, and acryloyloxyalkyloxy groups having 5 to 11
carbon atoms are particularly preferable.
Examples of the above-mentioned methacryloyloxyalkyloxy group
having 4 to 15 carbon atoms in total include a
methacryloyloxyethyloxy group, methacryloyloxybutyloxy group,
methacryloyloxydecyloxy group and the like, and, of these,
methacryloyloxyalkyloxy groups having 6 to 14 carbon atoms are
preferable, and methacryloyloxyalkyloxy groups having 6 to 12
carbon atoms are particularly preferable.
The molecular weight of a light-reaction type chiral agent of the
above-mentioned general formula (II) is preferably 300 or more.
Those showing high solubility with liquid crystalline compounds
described below are preferable, and those having a solubility
parameter SP value near that of the liquid crystalline compound are
more preferable.
Specific examples of a compound of the above-mentioned general
formula (II) include, but in the present invention are not limited
to, the following compounds (exemplified compounds (13) to (27)).
##STR10## ##STR11## ##STR12##
Next, examples of synthesizing compounds of the general formula
(II) will be described. A number in parentheses after a
light-reaction type chiral agent represents the number of one of
the above exemplified light-reaction type chiral agents
(exemplified compounds).
[Synthesis of Light-reaction Type Chiral Agent (14)]
4-methoxycinnamic acid (15 g, 0.084 mole) and dimethylformamide (2
to 3 drops) were dissolved in tetrahydrofuran (100 mL), and to this
was further added dropwise a solution prepared by dissolving oxalyl
chloride (10 mL, 0.13 mole) in tetrahydrofuran (50 mL), and they
were reacted for 2 hours. The solvent and excess oxalyl chloride in
the reaction solution were distilled off under reduced pressure.
Then, the solution was diluted with tetrahydrofuran (100 mL), and
to this was added isosorbide (5.5 g, 0.038 mole). To this was
further added dropwise pyridine (27 mL, 0.33 mole) dissolved in
tetrahydrofuran (50 mL) while stirring, and the mixture was stirred
for 3 hours. Then, to the reaction solution was added 10%
hydrochloric acid (100 mL) and ethyl acetate (200 mL) and this
mixture was stirred, and separated. A resulting organic layer was
washed once with saturated saline solution (100 mL), twice with
saturated sodium bicarbonate solution (100 mL) and twice with
saturated saline solution (100 mL) in this order, and dried over
magnesium sulfate. Further, the organic solvent was distilled off
under reduced pressure. Then, the solution was purified by silica
gel column chromatography using as a developing solvent a mixed
solution of n-hexane-ethyl acetate (3:2 v/v), and re-crystallized
(n-hexane-ethyl acetate) to obtain a colorless crystal (9.8 g,
56%).
Identification results (data) of the colorless crystal as obtained
above are shown below.
Melting point Tm=113.7.degree. C., [.alpha.].sub.D.sup.25
-158.degree. (c0.50, EtOAc).
.sup.1 H-NMR (CDCl.sub.3) .delta. (in ppm from tetramethylsilane)
7.75-7.60 (2H, dd), 7.50-7.45 (4H, dd), 6.94-6.88 (4H, dd),
6.40-6.25 (2H, dd), 5.36-5.26 (2H, m), 4.95 (1H, t), 4.60 (1H, d),
4.15-3.90 (8H, m), 3.85 (6H, s).
[Synthesis of Light-reaction Type Chiral Agent (17)]
Trans-4-courmaric acid (20 g, 0.12 mole) and potassium carbonate
(33 g, 0.24 mole) were dispersed in dimethylformamide (100 mL), and
to this mixture was added dropwise n-bromobutane (50 g, 0.37 mole)
while heating in an oil bath. After stirring for 3 hours, insoluble
components were filtrated off, and the remaining solution was
diluted with ethyl acetate (400 mL) and washed with saturated
saline solution (200 mL). Further, the organic solvent was
distilled off under reduced pressure. Then, to the remaining
solution was added a solution prepared by dissolving ethanol (100
mL) and potassium hydroxide (20 g, 0,36 mole) in water (50 mL), and
the mixture was refluxed for 1 hour. The reaction solution was
poured into diluted hydrochloric acid, and deposited crystal was
filtrated off and dissolved in chloroform (500 mL). A resulting
organic layer was washed with saturated saline solution, and dried
over magnesium sulfate. Further, the organic solvent was distilled
off under reduced pressure, and then recrystallized (n-hexane-ethyl
acetate) to obtain 4-n-butoxycinnamic acid (22.7 g, 84%) in the
form of a colorless crystal.
The resulting 4-n-butoxycinnamic acid (5 g, 0.023 mole) and
dimethylformamide (2 to 3 drops) were dissolved in tetrahydrofuran
(50 mL), and to this mixture was further added dropwise a solution
prepared by dissolving oxalyl chloride (2.9 mL, 0.034 mole) in
tetrahydrofuran (30 mL). These were reacted for 2 hours. The
solvent and excess oxalyl chloride in the reaction solution were
distilled off under reduced pressure. Then, the solution was
diluted with tetrahydrofuran (50 mL), and to this was added
isosorbide (1.5 g, 0.010 mol). To this was further added dropwise
pyridine (11 mL, 0.14 mole) dissolved in tetrahydrofuran (20 mL)
while stirring, and the mixture was stirred for 3 hours. Then, to
the reaction solution was added 10% hydrochloric acid (50 mL) and
ethyl acetate (100 mL) and this mixture was stirred, and separated.
A resulting organic layer was washed once with saturated saline
solution (50 mL) twice with saturated sodium bicarbonate solution
(50 mL) and twice with saturated saline solution (50 mL) in this
order, and dried over magnesium sulfate. Further, the organic
solvent was distilled off under reduced pressure, then purified by
silica gel column chromatography, using as a developing solvent a
mixed solution of n-hexane-ethyl acetate (2:1 v/v), and
re-crystallized (n-hexane-ethyl acetate) to obtain a colorless
crystalline powder (1.4 g, 25%).
Identification results (data) of the colorless crystalline powder
as obtained above are shown below.
Melting point Tm=132.4.degree. C., [.alpha.].sub.D.sup.25
-115.0.degree. (c0.10, EtOAc).
.sup.1 H-NMR (CDCl.sub.3): .delta. (in ppm from tetramethylsilane)
7.75-7.65 (2H, dd), 7.50-7.45 (4H, dd), 6.90-6.85 (4H, dd),
6.40-6.26 (2H, dd), 5.35-5.25 (2H, m), 4.94 (1H, t), 4.60 (1H, d),
4.13-3.95 (8H, m), 1.94-1.65 (4H, m), 1.55-1.44 (4H, m), 0.95 (6H,
t).
[Synthesis of Light-reaction Type Chiral Agent (24)]
Trans-4-courmaric acid (20 g, 0.12 mole), potassium iodide (24 g,
0.14 mole) and potassium carbonate (85 g, 0.62 mole) were dispersed
in dimethylformamide (200 mL) and water (100 mL), and to this
mixture was added dropwise 6-chlorohexanol (68 g, 0.50 mole) while
heating in an oil bath. After stirring for 3 hours, the solution
was diluted with ethyl acetate (400 mL) and washed with saturated
saline solution (400 mL). Further, the organic solvent was
distilled off under reduced pressure. Then, to the remaining
solution was added a solution prepared by dissolving ethanol (200
mL) and potassium hydroxide (20 g, 0,36 mole) in water (50 mL), and
this mixture was refluxed for 1 hour. The reaction solution was
poured into diluted hydrochloric acid, and deposited crystal was
filtrated off and then dried to obtain
4-(6-hydroxyhexyloxy)cinnamic acid (22 g, 64%) in the form of a
colorless crystalline powder.
The resulting 4-(6-hydroxyhexyloxy)cinnamic acid (6 g, 0.023 mole)
and N,N-dimethylaniline (6.6 g, 0.054 mole) were dissolved in
tetrahydrofuran (50 mL), and to this mixture was further added
dropwise a solution prepared by dissolving acryloyl chloride (4.4
g, 0.049 mole) in tetrahydrofuran (20 mL). After this addition, the
mixture was stirred for 4 hours. Then, the reaction solution was
poured into 10% hydrochloric acid, and deposited crystal was
filtrated off. The resulting coarse crystal was dissolved in ethyl
acetate (100 mL), and an organic layer was washed with saturated
saline solution and dried over magnesium sulfate. The organic
solvent was distilled off under reduced pressure, and then the
coarse crystal was re-crystallized (n-hexane-ethyl acetate) to
obtain 4-(6-acryloyloxyhexyloxy)cinnamic acid (3.9 g, 54%) in the
form of a colorless crystalline powder.
The resulting 4-(6-acryloyloxyhexyloxy)cinnamic acid (3 g, 9.4
mole) and dimethylformamide (2 to 3 drops) were dissolved in
tetrahydrofuran (50 mL), and to this mixture was further added
dropwise a solution prepared by dissolving oxalyl chloride (1.2 mL,
0.014 mole) in tetrahydrofuran (10 mL), and these were reacted for
2 hours. The solvent and excess oxalyl chloride in the reaction
solution were distilled off under reduced pressure. Then, the
solution was diluted with tetrahydrofuran (50 mL), and to this was
added isosorbide (0.6 g, 4.1 mmole). To this was further added
dropwise pyridine (4.5 mL, 0.056 mole) dissolved in tetrahydrofuran
(20 mL) while stirring, and the mixture was stirred overnight.
Then, to the reaction solution was added 10% hydrochloric acid (50
mL) and ethyl acetate (100 mL), and the mixture was stirred, and
separated. A resulting organic layer was washed once with saturated
saline solution (50 mL), twice with saturated sodium bicarbonate
solution (50 mL) and twice with saturated saline solution (50 mL)
in this order, and dried over magnesium sulfate. The organic
solvent was distilled off under reduced pressure, and then purified
by silica gel column chromatography, using as a developing solvent
a mixed solution of n-hexane-ethyl acetate (3:2 v/v), to obtain a
colorless crystalline powder (1.1 g, 38%).
Identification results (data) of the colorless crystalline powder
as obtained above are shown below.
Melting point Tm=70.5.degree. C., [.alpha.].sub.D.sup.25
-103.0.degree. (c0.11, EtOAc).
.sup.1 H-NMR (CDCl.sub.3): .delta. (in ppm from tetramethylsilane)
7.75-7.65 (2H, dd), 7.50-7.45 (4H, dd), 6.92-6.88 (4H, dd),
6.45-5.88 (8H, m), 5.35-5.25 (2H, m), 4.95 (1H, t), 4.60 (1H, d),
4.20-3.85 (8H, m), 1.94-1.65 (4H, m), 1.85-1.45 (16H, m).
A light-reaction type chiral agent of the above-mentioned general
formula (I) or (II) can cause a significant change of the twisting
power of the helical structure of a crystal. Further, in the case
of a structure in which one or more polymerizable bonding groups
have been introduced in the structure, the light-reaction type
chiral agent of the present invention can improve heat resistance
of a liquid crystal composition, a liquid crystal color filter or
an optical film containing a liquid crystal composition.
Further, the light-reaction type chiral agent of the present
invention can also be used together with a chiral agent having no
light reactivity, such as a chiral compound showing high dependency
of twisting power on temperature, or the like. The above-mentioned
known chiral agent having no light reactivity includes chiral
agents described, for example, in JP-A Nos. 2000-44451, 10-509726,
WO98/00428, JP-A Nos. 2000-506873 and 9-506088, "Liquid Crystals"
(1996, 21, 327), "Liquid Crystals" (1998, 24, 219) and the
like.
<Liquid Crystal Composition>
A liquid crystal composition contains at least one selected from
the above-mentioned light-reaction type chiral agents of the
present invention or a light-reaction type optically active
compound of the general formula (I). Embodiments further containing
at least one liquid crystalline compound (preferably, a nematic
liquid crystal compound) are preferable, and the above-mentioned
liquid crystalline compound may have a polymerizable group or may
not have a polymerizable group. Further, if necessary, other
components such as a polymerizable monomer, polymerization
initiator, binder resin, solvent, surfactant, polymerization
inhibitor, thickening agent, coloring matter, pigment, ultraviolet
absorber, gelling agent and the like may also be contained.
In the liquid crystal composition of the present invention,
particularly, it is preferable to also use a surfactant. For
example, an orientation condition at an air interface at the
surface of a layer can be sterically controlled and a selective
reflection wavelength having higher color purity can be obtained,
such as in cases of application of a liquid crystal composition in
the form of a coating solution to form a layer.
(Light-reaction Type Chiral Agent)
The liquid crystal composition of the present invention contains as
the light-reaction type chiral agent the above-mentioned
light-reaction type chiral agent of the present invention or a
light-reaction type optically active compound of the general
formula (I), and sterically controls the orientation structure of
the liquid crystal molecules and the helical structure of a liquid
crystalline compound therewith, which is preferably a nematic
liquid crystal compound, is changed by effecting light irradiation
in desired patterns and light amounts. In a system containing a
nematic liquid crystal compound, selective reflection colors in a
wide wavelength range can be manifested.
The content of the light-reaction type chiral agent in the liquid
crystal composition is not particularly restricted and can be
appropriately selected, and is preferably from about 2 to 30% by
weight.
(Liquid Crystalline Compound)
The liquid crystalline compound can be appropriately selected from
liquid crystal compounds having a refractive index anisotropy An of
0.10 to 0.40, polymer liquid crystal compounds, and polymerizable
liquid crystal compounds. For example, smectic liquid crystal
compounds and nematic liquid crystal compounds and the like are
listed, and among them, nematic liquid crystal compounds are
preferable. For example, a cholesteric liquid crystal composition
(cholesteric liquid crystal phase) can be obtained by using a
nematic liquid crystal compound as a liquid crystalline compound,
and using a light-reaction type chiral agent of the above-mentioned
general formula (I) or (II) together therewith.
The above-mentioned liquid crystalline compound can be oriented,
when it is in the liquid crystal condition of melting, by using an
oriented substrate on which orientation treatments such as a
rubbing treatment and the like have been performed for example.
Further, when liquid crystal condition is converted into solid
phase for fixing, a means such as cooling, polymerization or the
like can be used.
As specific examples of the above-mentioned liquid crystalline
compound, the following compounds are listed. However, they do not
limit the scope of the present invention. ##STR13##
In the above-mentioned formulae, n represents an integer from 1 to
1000.
In the above-mentioned exemplified compounds, those in which a
connecting group on an aromatic ring has been converted into one of
the following structures may be listed as suitable examples.
##STR14##
Among the above-mentioned compounds, liquid crystalline compounds
having a polymerizable group or cross-linkable group in the
molecule are preferable from the standpoint of securing of
sufficient hardening property and giving heat resistance of a
layer.
The content of the above-mentioned liquid crystalline compound is
preferably from 30 to 99.9% by weight, more preferably from 50 to
95% by weight based on the total solid content (by weight) of a
liquid crystal composition. When the above-mentioned content is
less than 30% by weight, orientation may be insufficient, and
particularly in the case of a cholesteric liquid crystal, desired
selective reflection colors may not be obtained.
(Polymerizable Monomer)
The liquid crystal composition of the present invention may contain
a polymerizable monomer therein, for the purpose of improving
extent of hardening, such as film strength or the like. When the
polymerizable monomer is used, it is possible that after the
twisting power of a liquid crystal has been changed (patterning) by
light irradiation (for example, after formation of a distribution
of selective reflection wavelengths), then the helical structure
thereof (selective reflection property) is fixed, and the strength
of the liquid crystal composition after fixing can be improved.
However, when the above-mentioned liquid crystalline compound has
an unsaturated bond in the same molecule, this addition is not
necessarily required.
The above-mentioned polymerizable monomer includes, for example,
monomers having an ethylenically unsaturated bond, and the like,
and specifically includes poly-functional monomers such as
pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and
the like.
Specific examples of the above-mentioned monomers having an
ethylenically unsaturated bond include, but in the present
invention are not limited to, the following compounds.
##STR15##
The amount of the above-mentioned polymerizable monomer added is
preferably from 0.5 to 50% by weight based on the total solid
content (by weight) of the liquid crystal composition. If the
addition amount is less than 0.5% by weight, sufficient hardening
property may not be obtained, and if over 50% by weight, the
orientation of liquid crystal molecules will be disturbed and
sufficient color development may not be obtained.
(Photopolymerization Initiator)
The liquid crystal composition of the present invention may also
contain a photopolymerization initiator and, by simultaneous use of
this photopolymerization initiator, it is possible that a
polymerization reaction of a polymerizable group will be promoted,
helical structure after helical pitch (twisting power) of the
liquid crystals has been changed by light irradiation will be
fixed, and the strength of the liquid crystal composition after
fixing will be improved. If a polymerization reaction using a
polymerizable crystalline compound is to be utilized for fixation
of the helical structure of the liquid crystal, the
photopolymerization initiator is preferably added.
For example, if the liquid crystal phase is a cholesteric liquid
crystal phase, desired helical pitch can be obtained stably, and
selective reflection colors having high color purity can be
secured.
The above-mentioned photopolymerization initiator can be
appropriately selected from known compounds, and examples thereof
include p-methoxyphenyl-2,4-bis(trichloromethyl)-s-triazine,
2-(p-butoxystyryl)-5-trichloromethyl-1,3,4-oxadiazole,
9-phenylacridine, 9,10-dimethylbenzphenazine,
benzophenone/Michler's ketone,
hexaarylbiimidazole/mercaptobenzimidazole, benzyldimethylketal,
thioxanthone/amine, triarylsulfoniumhexafluorophosphate and the
like, bisacylphosphine oxides described in JP-A No. 10-29997 such
as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and the like,
acylphosphine oxides described in DE4230555 and the like, of
Lucirin TPO and the like, and the like.
The amount of the above-mentioned photopolymerization initiator
added is preferably from 0.1 to 20% by weight, more preferably from
0.5 to 5% by weight based on the total solid content (by weight) of
the liquid crystal composition. If the addition amount is less than
0.1% by weight, a longer period of time may be necessary due to low
hardening efficiency in light irradiation, and if over 20% by
weight, light percent transmission may be inferior from the
ultraviolet region the to visible region.
(Other Components)
Further, as other components, a binder resin, solvent, surfactant,
polymerization inhibitor, thickening agent, coloring matter,
pigment, ultraviolet absorber, gelling agent and the like can also
be added.
The above-mentioned binder resin includes, for example, polystyrene
compounds such as polystyrene, poly-.alpha.-methylstyrene and the
like, cellulose resins such as methylcellulose, ethylcellulose,
acetylcellulose and the like, acidic cellulose derivatives having a
carboxyl group on a side chain, acetal resins such as
polyvinylformal, polyvinylbutyral and the like, and methacrylic
acid copolymers, acrylic acid copolymers, itaconic acid copolymers,
crotonic acid copolymers, maleic acid copolymers,
partially-esterified maleic acid copolymers and the like described
in JP-A No. 59-44615, JP-B Nos. 54-34327, 58-12577 and 54-25957,
JP-A Nos. 59-53836 and 59-71048.
Homopolymers of alkyl acrylates and homopolymers of alkyl
methacrylates are also listed, and, as examples thereof, those in
which the alkyl group is a methyl group, ethyl group, n-propyl
group, n-butyl group, iso-butyl group, n-hexyl group, cyclohexyl
group, 2-ethylhexyl group or the like are listed.
In addition, those obtained by adding an acid anhydride to a
polymer having a hydroxyl group, and a benzyl
(meth)acrylate/(meth)acrylic acid copolymer, multiple copolymers of
benzyl (meth)acrylate/(meth) acrylic acid/other monomers, and the
like, are listed.
The content of the binder resin in the liquid crystal composition
is preferably from 0 to 50% by weight, more preferably from 0 to
30% by weight. If the above-mentioned content is over 50% by
weight, the orientation of the liquid crystalline compound may be
insufficient.
In the liquid crystal composition of the present invention, it is
preferable to use a surfactant together with a light-reaction type
chiral agent and a liquid crystalline compound from the standpoint
of more improvement of color purity of a hue that is selectively
reflected. As the surfactant, surfactants exerting an exclusion
volume effect are preferable. Here, exertion of an exclusion volume
effect means that when a layer containing a liquid crystal
composition is formed by application, a spatial orientation
condition at the air interface on the layer surface is sterically
controlled. Specifically, nonionic surfactants are preferable, and
surfactants appropriately selected from know nonionic surfactants
can be used.
The above-mentioned polymerization inhibitor can be added for the
purpose of improving storability. For example, hydroquinone,
hydroquinone monomethyl ether, phenothiazine, benzoquinone and
derivatives thereof are listed. The amount of the polymerization
inhibitor added is preferably from 0 to 10% by weight, and more
preferably from 0 to 5% by weight based on the above-mentioned
polymerizable monomer.
The liquid crystal composition of the present invention can be
prepared by dissolving or dispersing components in a suitable
solvent, and can be molded into any form or formed on a supporting
substrate or the like. As the above-mentioned solvent, for example,
2-butanone, cyclohexanone, methylene chloride, chloroform and the
like are listed.
<Method of Changing Twist Structure of Liquid Crystal>
As described above, the liquid crystal composition of the present
invention contains a light-reaction type chiral agent or a
light-reaction type optically active compound, and, in the method
of changing the twist structure of the liquid crystal of the
present invention, the above-mentioned liquid crystal composition
of the present invention is irradiated with light while changing
light amounts to cause a change of twisting power of the liquid
crystal and to form regions having different twist structure of the
liquid crystals. That is, by irradiating the liquid crystal
composition with light using desired light amounts in desired
patterns, the twist structure of the liquid crystal, namely, extent
of twisting of helices (twisting power; HTP) can be changed, and
selective reflection colors manifested by the liquid crystal
depending on the twisting power can be changed optionally.
Particularly, when the liquid crystal phase is a cholesteric liquid
crystal phase, selective reflection colors manifested by the liquid
crystals depending on twisting power can be changed optionally.
When change rate of this twisting power is large, color width of
selective reflection colors which can be selectively reflected by
the liquid crystal is wide, and selective reflection in a wide
wavelength range including three primary colors (B, G, R) can be
obtained. This is particularly important in that the three primary
colors RGB can be displayed with high color purity. In this point,
particularly the above-mentioned light-reaction type optically
active compound and light-reaction type chiral agent of the general
formula (I) or (II) can significantly change the twisting power of
the helical structure of the liquid crystals. Consequently, by use
of a liquid crystal composition containing this compound and/or
chiral agent, hues in a wide range including blue (B), green (G)
and red (R) can be displayed, and three primary colors having
excellent color purities can be obtained.
Specific procedures are described below.
When a liquid crystal composition is irradiated with light having a
certain wavelength, a light-reaction type chiral agent or
light-reaction type optically active compound therewith causes a
change of the helical structure (twist angle) of a liquid crystal
based on irradiation strength. By this structural change, different
selective reflection colors are displayed and image-wise patterns
are formed (patterning). In the case of a cholesteric liquid
crystal composition, different selective reflection colors are
shown by this structural change. Accordingly, light irradiation is
effected using irradiation strength changed for each desired range,
orientation is effected (a plurality of colors are displayed)
corresponding to irradiation strength, and, for example, by
conducting exposure via a mask for exposure made with light percent
transmissions varied image-wise, images can be formed by one-time
light irradiation. That is, colored regions having different
selective reflections can be formed simultaneously.
Further, a compound of the general formula (I) or (II) can
significantly change the helical pitch of the liquid crystals, and
in the case of a cholesteric liquid crystal composition, colored
regions that are formed show a wide range of selective reflection
colors, and three primary colors BGR, which are excellent in color
purity, can be formed. This light irradiation can be conducted
without specific limitation by methods which can change irradiation
strength at each desired region, in addition to the method using a
mask for exposure.
When a liquid crystal color filter and an optical film and the like
described later are formed, exposure is effected image-wise with
light having a certain wavelength as described above to cause
patterning. Then, light irradiation is further conducted to cause
photopolymerization of a polymerizable group in a liquid crystal
composition to harden the composition, and the helical structures
of liquid crystals are fixed at desired selective reflection
colors. Details of this formation method are described later.
As the light source used for light irradiation, light sources
emitting ultraviolet radiation are preferable since they have high
energy, and structural change and polymerization of a liquid
crystal compound can be effected quickly. For example, a high
pressure mercury lamp, metal halide lamp, Hg--Xe lamp and the like
are listed. Further, it is preferable that the light source has a
function which can change light amount.
As described above, by use of a light-reaction type optically
active compound or a light-reaction type chiral agent of the
general formula (I) or (II), the twisting power of the helical
structure of a liquid crystal depending on light amount can be
significantly changed. Therefore, for example, in the case of a
cholesteric liquid crystal phase using a nematic liquid crystal
composition as the liquid crystalline compound, the color width of
selective reflection colors which can be manifested by the liquid
crystal is enlarged, and three primary colors, blue (B), green (G)
and red (R), excellent in color purity can be obtained.
By utilizing the large change rate of helical pitch caused in the
liquid crystal phase by light irradiation because of the
light-reaction type optically active compound or light-reaction
type chiral agent of the above-mentioned general formula (I) or
(II), liquid color filters, and circular polarization separation
films, glasses for stereoscopic vision, polarization masks and the
like, which are used as optical films can be formed as described
later. Further, this can be applied also to wide-region switchable
mirrors, recording media of light-recording types, and the like.
Patterning of polarization conditions and patterning of helical
pitch by doping the liquid crystal composition of the present
invention into a ferroelectric liquid crystal, antiferroelectric
liquid crystal or TGB phase become possible. Further, use as a
usual optical active compound is of course possible, and
application to a helical structure-inducing agent for STN elements
and TN elements is also possible.
In the liquid crystal composition of the present invention,
non-chiral azo-based or styrene-based compounds which are
isomerized by light can also be compounded, and change rate of
helical pitch by light irradiation may be further increased in some
cases.
A liquid crystal color filter, optical film and recording medium
will be illustrated in detail below.
<Liquid Crystal Color Filter>
The liquid crystal color filter of the present invention contains
at least one selected from the above-mentioned light-reaction type
optically active compound or light-reaction type chiral agents of
the present invention, further, embodiments containing at least one
liquid crystalline compound are preferable, and, as this liquid
crystalline compound, a nematic liquid crystal compound is most
preferable. Further, if necessary, other components listed for the
above-mentioned liquid crystal composition of the present
invention, such as polymerizable monomers, photopolymerization
initiators, surfactants exerting an exclusion volume effect, and
the like, can be contained. A filter can be produced by light
irradiation using desired light amounts and patterns selected
appropriately based on the above-mentioned method for changing the
twist structure of liquid crystals.
The liquid crystal color filter of the present invention will be
described in detail below by explanation of a method of producing a
liquid crystal color filter.
The liquid crystal color filter of the present invention can be
produced by using a material selected appropriately from the
above-mentioned liquid crystal compositions of the present
invention and known compositions containing a compound of the
above-mentioned general formula (I) or (II).
In this case, the color filter may be in the form of a sheet
constituted only of the above-mentioned liquid crystal composition,
or comprising a desired substrate or temporary substrate carrying
thereon a layer containing the liquid crystal composition (liquid
crystal layer), and further, may comprise other layers (films) such
as an orientation film, protective film and the like. In the latter
case, two or more liquid crystal layers can be laminated. In this
case, the exposure process described below is used a number of
times.
As the above-mentioned nematic liquid crystal composition,
polymerizable monomer, photopolymerization initiator and other
components, the same compounds as can be used in the
above-mentioned liquid crystal composition of the present invention
can be used, and the contents, preferable ranges and the like are
as in the case of the above-mentioned liquid crystal composition.
It is preferable to simultaneously use a surfactant that exerts an
exclusion volume effect.
Further, the content of a compound of the above-mentioned general
formula (I) or (II) in the liquid crystal composition constituting
the liquid crystal color filter is also the same as in the
above-mentioned liquid crystal composition of the present
invention.
The liquid crystal color filter of the present invention can be
suitably produced, for example, from the above-mentioned liquid
crystal composition of the present invention.
A method of producing the liquid crystal color filter is not
particularly restricted and, for example, a production method can
include at least one process in which exposure is conducted
image-wise using a first light to effect patterning, then a second
light to effect photopolymerization and cause hardening
(hereinafter referred to as "exposure process" in some cases).
Further, depending on a production embodiments selected, the filter
may be formed via a process in which an orientation treatment is
appropriately performed on a contact surface with the liquid
crystal composition (orientation treatment process), a process in
which the liquid crystal layer is transferred and formed by
close-adhesion and releasing (transfer process), a process in which
a cholesteric liquid crystal composition is applied to form a
liquid crystal layer (application process), and other
processes.
One specific embodiment using a cholesteric liquid crystal
composition is shown below as an example of the above-mentioned
production method including an exposure process.
[Exposure Process]
In this exposure process, each of patterning and fixation
(hardening by polymerization) of a liquid crystal compound is
conducted by light irradiation. Namely, patterning is conducted by
exposure image-wise using a first light having a wavelength which
can sensitize a light-reaction type optically active compound or
light-reaction type chiral agent at high sensitivity. Then, the
liquid crystal composition is hardened by photopolymerization using
a second light which can sensitize a polymerization initiator at
high sensitivity, to fix the helical structure of the liquid
crystal composition for desired selective reflection colors.
When the liquid crystal composition is irradiated with the
above-mentioned first light, the light-reaction type optically
active compound or light-reaction type chiral agent therein is
sensitized depending on illuminance of the light to change the
helical structure of the liquid crystal compound. By this
structural change, different selective reflection colors are
manifested and image-wise patterns are formed. Therefore, light
irradiation is conducted while changing irradiation strength for
respective desired regions, and a plurality of colors are
manifested corresponding to irradiation strengths. For example, by
conducting exposure via a mask for exposure produced for changing
light percent transmission image-wise, images can be formed by
one-time light irradiation. That is, colored regions having
different selective reflections can be formed simultaneously. This
image can further be irradiated with the second light to be
hardened (fixed), giving the liquid crystal color filter.
As the wavelength of the above-mentioned first light, wavelengths
in the wavelength range in which the light-reaction type optically
active compound or light-reaction type chiral agent is sensitized,
particularly wavelengths adjacent to a light-sensitization peak
wavelength of the optically active compound or the chiral agent,
are preferable since sufficient patterning sensitivity is obtained.
As the wavelength of the second light, wavelengths in a wavelength
range in which the polymerization initiator is sensitized,
particularly wavelengths adjacent to the light-sensitization peak
wavelength of the polymerization initiator, are preferable since
sufficient photopolymerization sensitivity is obtained.
The illuminances of the first and second lights (irradiation
degree) are not particularly restricted, and can be appropriately
selected depending on materials used, so as to sufficiently obtain
light sensitivities in patterning and photopolymerization. As light
sources used in irradiation of the first and second lights, the
same light sources as those which can be used for irradiation of
the above-mentioned liquid crystal composition can be used.
More specifically, production methods of the following first and
second embodiments may be permissible, and a color filter can be
produced more preferably by one of these two embodiments.
[First Embodiment] (1) Process in which a liquid crystal
composition in the form of an application solution is provided on a
temporary substrate to form a transferring material having at least
a liquid crystal layer
The above-mentioned liquid crystal composition in the form of an
application solution can be prepared by dissolving or dispersing
components in a suitable solvent. Here, as this solvent, for
example, 2-butanone, cyclohexanone, methylene chloride, chloroform
and the like are listed. In production of a liquid crystal color
filter, a cholesteric liquid crystal composition is preferable.
Between the above-mentioned liquid crystal layer and temporary
substrate, a cushioning layer containing a thermoplastic resin and
the like can also be provided, when extraneous substances and the
like are present on a receiving body or the like, from the stand
point of securing close-adhesion in transferring. It is preferable
to perform orientation treatments (orientation treatment process)
such as rubbing and the like on the surface of the cushioning layer
and the like. (2) Process in which the above-mentioned transferring
material is laminated on a substrate permitting light
transmission
An image-receiving material having an image-receiving layer on a
substrate may also be used, in addition to the above-mentioned
substrate permitting light transmission. Further, a liquid crystal
composition may be directly applied and formed on a substrate
without using the above-mentioned transferring material
(application process). The application method can be appropriately
selected from known application methods using a bar coater, spin
coating and the like. Of these, a transferring method is preferable
from the standpoints of material loss and cost. (3) Process in
which transferring material is peeled from substrate permitting
light transmission, and cholesteric liquid crystal layer is formed
on the above-mentioned substrate (transferring process)
The above-mentioned liquid crystal layer can also be constituted of
plural layers further laminated after the following process (4) (4)
Process in which cholesteric liquid crystal layer is irradiated
with ultraviolet radiation having illuminance of .nu..sup.1 via
mask for exposure to form picture element pattern showing selective
reflection color, and this is irradiated with ultraviolet radiation
having illuminance of .nu..sup.2 to harden layer (exposure
process)
[Second Embodiment] (1) Process in which liquid crystal composition
is directly provided on substrate constituting color filter, to
form liquid crystal layer
In this process, a liquid crystal composition prepared in the form
of an application solution in the same manner as described above
can be applied by a known application method using a bar coater,
spin coater or the like, to form a liquid crystal layer.
Further, between the above-mentioned cholesteric layer and
substrate, the same orientation film as described above may also be
formed. It is preferable to perform orientation treatments
(orientation treatment process) such as rubbing and the like on the
surface of the orientation film. (2) Same exposure process as
process (4) in the above-mentioned first embodiment
The thickness of the liquid crystal layer functioning as the liquid
color filter (liquid crystal composition in the form of a sheet) is
preferably from 1.5 to 5 .mu.m.
Further explanations are provided below using FIG. 1. FIG. 1 is
sectional views showing one embodiment of a process of producing
the liquid crystal color filter of the present invention.
First, the above-mentioned components are dissolved in a suitable
solvent, to prepare a cholesteric liquid crystal composition in the
form of an application solution. Herein, the components and solvent
are as described above.
As illustrated in FIG. 1A, a substrate 10 (hereinafter, also
referred to as "temporary substrate") is prepared, and on this
substrate 10, for example, an acrylic resin, polyester,
polyurethane or the like is applied to form a cushioning layer
(thermoplastic resin layer) 12, and further an orientation film 14
composed of polyvinyl alcohol and the like is laminated. On this
orientation film, rubbing treatment is performed as shown in FIG.
1B. Though this rubbing treatment is not necessarily required, an
orientation property can be more improved when the rubbing
treatment is conducted.
Then, as shown in FIG. 1C, on the above-mentioned orientation film
14, a cholesteric liquid crystal composition in the form of an
application solution is applied and dried to form a cholesteric
liquid crystal layer 16. Then, a cover film 18 is provide on this
cholesteric liquid crystal layer 16 to provide a transferring
material. Hereinafter, this transferring material is referred to as
a transferring sheet 20.
On the other hand, as shown in FIG. 1D, another substrate 22 is
prepared, an orientation film 24 is formed on this substrate as
described above, and rubbing treatment is performed on the surface
thereof. Hereinafter, this is referred to as a substrate 26 for a
color filter.
Next, the cover film 18 of the transferring sheet 20 is peeled,
then, as shown in FIG. 1E, the surface of the cholesteric liquid
crystal layer 16 of the transferring sheet 20 and the surface of
the orientation film 24 of the substrate 26 for the color filter
are joined so that they are in contact with each other, and
laminated by passing through a roll, rotating along a direction
represented by an arrow in the figure. Then, as shown in FIG. 1F,
peeling is caused between the orientation film 14 and the
cushioning layer 12 of the transferring sheet 20, and the
cholesteric liquid crystal layer is transferred together with the
orientation film 14 onto the substrate 26 for the color filter. In
this case, the cushioning layer 12 need not necessarily be peeled
together with the temporary substrate 10.
After transferring, as shown in FIG. 1G, an exposure mask 28 having
a plurality of regions having different light percent transmissions
is placed above the orientation film 14, and the cholesteric liquid
crystal layer 16 is irradiated pattern-wise with a first light via
this mask 28. The cholesteric liquid crystal layer 16 contains
liquid crystal compounds, chiral compounds and the like such that
helical pitch varies depending on the light irradiation amount, and
structures having different helical pitches are formed such that,
for example, a region which reflects green color (G) and allows
transmission of blue color (B) and red color (R), a region which
reflects blue color (B) and allows transmission of green color (G)
and red color (R), and a region which reflects red color (R) and
allows transmission of green color (G) and blue color (B) are
formed for each pattern.
Next, as shown in FIG. 1H, the cholesteric liquid crystal layer 16
is further irradiated with ultraviolet radiation at a different
irradiation strength than in the light irradiation in the
above-mentioned process of FIG. 1G, to fix patterns. Then,
unnecessary portions on the cholesteric liquid crystal layer 16
(for example, remaining portions of the cushioning layer,
intermediate layer and the like, and unexposed portions) can be
removed by using 2-butanone, chloroform or the like, to form a
cholesteric liquid crystal layer having reflection regions of R, G
and B as shown in FIG. 1I.
The method shown in FIG. 1 is one embodiment of a method of
producing a color filter according to a lamination mode, and it may
also be a production method according to an application mode in
which a liquid crystal layer is directly applied and formed on a
substrate for a color filter. In this case, a cholesteric liquid
crystal layer is applied on the orientation film 24 of the
substrate 26 for the color filter shown in FIG. 1D, dried, and then
the processes shown in FIGS. 1G to 1I as described above are
carried out sequentially.
These processes, transferring materials used, materials of a
substrate and the like, are described in detail in specifications
of Japanese Patent Application Nos. 11-342896 and 11-343665
submitted previously by the present inventors.
As described above, when a liquid crystal composition containing a
light-reaction type optically active compound of the general
formula (I) or a light-reaction type chiral agent of the present
invention is used, the change rate of the twisting power of the
helical structure of liquid crystals based on light amounts is
large. Consequently, color width of selective reflection colors
which can be manifested by the liquid crystals is enlarged, and a
liquid crystal color filter composed of three primary colors, blue
(B), green (G) and red (R), excellent in color purities can be
obtained.
<Optical Film>
The optical film of the present invention contains at least one
selected from the above-mentioned light-reaction type optically
active compounds or light-reaction type chiral agents of the
present invention. Embodiments further containing at least one
liquid crystalline compound (preferably, a nematic liquid crystal
compound) are preferable. Optical wavelengths can be selected as
desired in a wide wavelength range. Further, the optical film of
the present invention contains, if necessary, other components as
listed for the above-mentioned liquid crystal composition of the
present invention such as polymerizable monomers,
photopolymerization initiators, and surfactants exerting an
exclusion volume effect and the like. This film can be produced by
conducting light irradiation with desired patterns and light
amounts selected appropriately, based on the above-mentioned
"method for changing twist structure of liquid crystal".
The optical film of the present invention can be produced by using
a material selected appropriately from the above-mentioned liquid
crystal compositions of the present invention and known
compositions containing a compound of the above-mentioned general
formula (I) or (II). Here, the form of the optical film is not
particularly restricted, and may be any of a sheet constituted only
of the above-mentioned liquid crystal composition, a desired
substrate or temporary substrate carrying thereon a layer
containing the liquid crystal composition (liquid crystal layer),
and other forms, and further, may comprise other layers (films)
such as an orientation film, protective film and the like.
As the above-mentioned liquid crystalline compound, polymerizable
monomer, photopolymerization initiator and other components, the
same compounds as can be used in the above-mentioned liquid crystal
composition of the present invention can be used, and the contents,
preferable ranges and the like are as in the case of the
above-mentioned liquid crystal composition. Further, the content of
a compound of the above-mentioned general formula (I) or (II) in
the liquid crystal composition constituting the optical film is
also be same as in the above-mentioned liquid crystal composition
of the present invention.
The optical film of the present invention can be preferably
produced using, for example, the above-mentioned liquid crystal
composition of the present invention.
This method of producing an optical film can be approximately the
same method as for the above-mentioned liquid crystal color filter,
and may also be a method containing the above-mentioned exposure
process at least one time. Further, depending on production
embodiments selected, an optical filter may be formed via a process
such as the above-mentioned orientation treatment process,
transferring process, application process and the like.
More specifically, an optical filter can also be produced by
approximately the same method as the production methods of the
above-mentioned first embodiment and second embodiment.
As described above, when a liquid crystal composition containing a
light-reaction type optically active compound or a light-reaction
type chiral agent of the general formula (I) or (II) is used, the
twisting power of the helical structure of liquid crystals with
light amount can be varied significantly. Consequently, an optical
film of a non-light absorption type can be obtained. For example,
the liquid crystal phase is a cholesteric liquid crystal phase, the
color width of selective reflection of the liquid crystals is
large, and an optical film having a variety of selective reflection
colors, an optical film composed of primary colors (B, G, R)
excellent in color purities, or the like can be obtained.
<Recording Medium>
The recording medium of the present invention contains at least one
selected from the above-mentioned light-reaction type optically
active compound or light-reaction type chiral agents of the present
invention, and embodiments further containing at least one liquid
crystalline compound (preferably, nematic liquid crystal compound)
are preferable. Further, the recording medium of the present
invention contains, if necessary, other components as listed for
the above-mentioned liquid crystal composition of the present
invention such as polymerizable monomers, photopolymerization
initiators, and surfactants exerting an exclusion volume effect and
the like, and the like.
The form of the recording medium of the present invention is not
particularly restricted, and may be a sheet constituted only of a
liquid crystal composition, or a desired support or temporary
support (hereinafter, referred to as "support and the like")
carrying thereon a layer comprising a liquid crystal composition
containing a light-reaction type optically active compound or a
light-reaction type chiral agent (liquid crystal layer). Here, the
liquid crystal composition can be appropriately selected from the
above-mentioned liquid crystal compositions of the present
invention and known compositions containing a compound of the
above-mentioned general formula (I) or (II). Further, other layers
(films) such as an orientation film, protective film and the like
may also be provided.
As the above-mentioned liquid crystalline compound, polymerizable
monomer, photopolymerization initiator and other components, the
same compounds as can be used in the above-mentioned liquid crystal
composition can be used, and the contents, preferable ranges and
the like are as in the case of the liquid crystal composition.
Further, the content of a compound of the above-mentioned general
formula (I) or (II) in a liquid crystal composition constituting a
recording medium is also be same as in the above-mentioned liquid
crystal composition of the present invention.
The recording medium of the present invention can be preferably
produced by providing the above-mentioned liquid crystal
composition of the present invention on a support and the like, for
example.
As the method of producing the liquid crystal composition on the
support and the like, there are (1) a method in which a
transferring material comprising a temporary support carrying
thereon a liquid crystal layer containing the liquid crystal
composition of the present invention is used, and the liquid
crystal layer is transferred onto a support, (2) a method in which
a liquid crystal composition prepared in the form of an application
solution is directly applied on the support and the like, and other
methods.
In the above-mentioned methods (1) and (2), transferring materials
and application methods and the like can be adapted according to
the embodiments exemplified for the above-mentioned liquid crystal
composition of the present invention (first and second embodiments)
and the explanations of FIG. 1.
The recording medium of the present invention produced as described
above can be irradiated with light at desired patters and light
amounts appropriately selected to form an image based on the change
rate of the twisting power of a liquid crystal, and, particularly
in the case of a cholesteric liquid crystal, can be irradiated to
form a color image formed by selective reflection colors determined
by the change rate of the helical pitch. The formation of the image
may be conducted based on the above-mentioned "method for changing
twist structure of liquid crystal" and "method for fixing twist
structure of liquid crystal".
In addition, when a light-reaction type optically active compound
or a light-reaction type chiral agent of the general formula (I) or
(II) is used as a chiral agent which changes the structure of a
liquid crystal, the change rate of the twisting power of the
helical structure of the liquid crystal depending on light amount
is large. Consequently, images having a wide color reproduction
range can be formed and, particularly in the case of a cholesteric
liquid crystal, a width of hues selectively reflected by a liquid
crystal can be enlarged, and multi-color images having high color
purities can be formed. Further, high change rate of the twisting
power also contributes significantly to an increase in sensitivity
(increase in speed) in forming images.
Further, by using, for example, a polymerizable liquid crystal
compound or a polymerizable monomer a liquid crystal after
patterning can be fixed, and images having sufficiently excellent
image stability can be formed.
As the light sources used in irradiation or fixing, the same light
sources as those which can be used for the above-mentioned liquid
crystal composition of the present invention can be used, giving
preferable photorecording.
As described above, when a light-reaction type optically active
compound or a light-reaction type chiral agent of the general
formula (I) or (II) is used as a chiral agent which changes the
helical structure of a liquid crystal molecule, the twisting power
(twist angle) of liquid crystals can be significantly changed.
Particularly in the case of a cholesteric liquid crystal using a
nematic liquid crystal compound, the selective reflection
wavelength range obtained by light irradiation is enlarged, and
consequently color purities of three primary colors can also be
enhanced. As a result, selectivity and clearness of the hues of the
liquid crystals increase, and, particularly in a liquid crystal
color filter, optical film or the like, clear and brilliant color
images can be displayed, and in a recording medium, images of
multiple hues can be formed.
EXAMPLES
The following examples further illustrate the present invention,
but do not limit the scope of the present invention. In the
examples, "parts" and "%" are all "parts by weight" and "% by
weight".
Example 1
Measurement of Change of Helical Pitch by Light Irradiation
2 parts of a light-reaction type chiral agent of the present
invention (exemplified compound (6)) synthesized by a method
analogous to the above-mentioned synthesis method and 98 parts of a
nematic liquid crystal composition (ZLI-1132, manufactured by
Merck) were mixed, and poured into a wedge type cell (glass
thickness 1.1 mm, blue plate) on which uni-axial orientation
treatment had been performed by a polyimide orientation film. Here,
helical pitch at room temperature was measured using a polarization
microscope and was found to be 1.47 .mu.m. This was calculated in
terms of helical twisting power (HTP) to give a value of 34
.mu.m.sup.-1.
Next, the above-mentioned wedge type cell was irradiated with
ultraviolet radiation for 3 minutes at an irradiation strength of
300 mW/cm.sup.2 from a high pressure mercury lamp. After
irradiation, helical pitch at room temperature was measured in the
same manner as described above, to find a pitch changed to 2.8
.mu.m. This was calculated in terms of HTP to give a value of 18
.mu.m.sup.-1. Therefore, the change rate of HTP was 1.89.
As described above, the twisting power of helices (HTP) could be
significantly changed by irradiation with ultraviolet radiation.
Further, the twist direction before and after irradiation with
ultraviolet radiation was confirmed by a contact method and was
found to be right-twisting both before and after irradiation.
Example 2
Production of Wide Band Circular Polarization Reflection Plate
(1) Preparation of Substrate
On a glass substrate, a polyimide orientation film (LX-1400,
manufactured by Hitachi Chemical Dupont) application solution was
applied by a spin coater, dried for 5 minutes in an oven at
100.degree. C., and then baked for 1 hour in an oven at 250.degree.
C. to form an orientation film. Further, the surface of the film
was subjected to orientation treatment by rubbing treatment to
produce a glass substrate equipped with an orientation film.
(2) Production
On the orientation film of the glass substrate equipped with the
orientation film obtained above, an application solution prepared
by the following recipe was applied by a bar coater, and kept for 5
minutes on a hot plate at 110.degree. C., and then irradiated with
light by an ultrahigh pressure mercury lamp via a band pass filter
having a light source center wavelength at 365 nm for 3 minutes, at
the same temperature. The following light-reaction type chiral
agent of the present invention (exemplified compound (5)) was
synthesized by a method analogous to the above-mentioned synthesis
method.
Next, the plate was kept in a dark place for 5 minutes while being
maintained at 110.degree. C. Then the band pass filter was removed,
and the whole surface was irradiated with light by the same
ultrahigh pressure mercury lamp as described above at an
irradiation energy of 500 mJ/cm.sup.2, while spraying a nitrogen
gas, to give hardening by polymerization. As described above, a
circular polarization reflection plate was produced.
[Recipe of application solution] ##STR16## 42 parts by weight
##STR17## 42 parts by weight Exemplified compound (5):
light-reaction type optically active compound (chiral agent)
##STR18## 13 parts by weight ##STR19## 2 parts by weight ##STR20##
5 parts by weight Chloroform 400 parts by weight
The circular polarization reflection plate obtained above
manifested selective reflections in a wide wavelength range ranging
from 450 nm to 680 nm, that is, had a band property sufficient for
a wide-band circular polarization reflection plate. Further, right
circular polarization reflectance at a selective reflection
wavelength of 550 nm was 95%.
Example 3
Production of Liquid Crystal Color Filter
(1) Preparation of Filter Substrate
On a glass substrate, a polyimide orientation film (LX-1400,
manufactured by Hitachi Chemical Dupont) application solution was
applied by a spin coater, dried for 5 minutes in an oven at
100.degree. C., and then baked for 1 hour in an oven at 250.degree.
C. to form an orientation film. Further, the surface of the film
was subjected to orientation treatment by rubbing treatment to
produce a glass substrate equipped with an orientation film.
(2) Production of Filter Layer
On the orientation film of the glass substrate equipped with the
orientation film obtained above, an application solution for a
photosensitive resin layer prepared by the following recipe was
applied by a spin coater, and dried for 2 minutes in an oven at
100.degree. C. to form a photosensitive resin layer. The following
light-reaction type chiral agent of the present invention
(exemplified compound (2)) was synthesized by the above-mentioned
synthesis method.
[Recipe of application solution for photosensitive resin layer]
##STR21## 42 parts by weight ##STR22## 42 parts by weight ##STR23##
16 parts by weight Exemplified compound (2): light-reaction type
optically active compound (chiral agent) ##STR24## 8 parts by
weight ##STR25## parts by weight Dipentaerythritol hexaacrylate 3
parts by weight Chloroform 400 parts by weight
Next, the plate was kept for 5 minutes on a hot plate of
100.degree. C. so as to give contact at the surface of the glass
substrate, to cause color development of the photosensitive resin
layer. Further, on this photosensitive resin layer, an ultrahigh
pressure mercury lamp was placed via a photomask carrying regions
having different transmittances at three grades (0%, 46%, 92%) and
being arranged corresponding to blue picture elements, green
picture elements and red color elements, and a band pass filter
having a central wavelength of 365 nm. The resin layer was
irradiated with light by the ultrahigh pressure mercury lamp though
the photomask and band pass filter, to realize patterning. At this
stage, the irradiation energy was 300 mJ/cm.sup.2 formed picture
elements and the irradiation strength was 30 mW/cm.sup.2.
Next, the photomask and band pass filter were removed, and the
layer was irradiated on the whole surface with light by the same
ultrahigh pressure mercury lamp as described above at an
irradiation energy of 500 mJ/cm.sup.2, while spraying a nitrogen
gas, to give hardening by polymerization. Further, for promoting
the degree of hardening of the filter part (photosensitive resin
layer), the layer was baked for 20 minutes in an oven at
220.degree. C., to obtain a color filter having patterns of red
picture elements, green picture elements and blue picture elements
formed therein.
In the above-mentioned patterning, the helical pitch of liquid
crystals (twisting power of liquid crystals) could be significantly
changed by irradiation and picture element patterns of a red color,
green color and blue color having high color purities could be
formed.
Example 4
Production of Optical Compensation Film for STN Element
On triacetylcellulose (TAC) having a thickness of 80 .mu.m, a
polyethylene vinyl alcohol (PVA) film having a saponification
degree of 99.5% was formed by a bar coat method, and heated at
110.degree. C. for 3 minutes. Rubbing treatment was performed on
this PVA film. Further, an application solution prepared by the
following recipe was applied on the PVA film with a bar coater
while heating, and this was dried in an oven at 120.degree. C. for
3 minutes to form a film. The following light-reaction type chiral
agent of the present invention (exemplified compound (7)) was
synthesized by the above-mentioned synthesis method.
[Recipe of application solution] ##STR26## 42 parts by weight
##STR27## 42 parts by weight Exemplified compound (7):
light-reaction type optically active compound (chiral agent)
##STR28## 0.5 parts by weight ##STR29## 3 parts by weight
Chloroform 400 parts by weight
Next, the film was polymerized to be hardened by irradiation over
the film with ultraviolet radiation using an high pressure mercury
lamp (irradiation energy 300 mJ/cm.sup.2) at 100.degree. C., to
produce an optical compensation film for an STN element
(hereinafter, referred to as "STN compensation film"). The film
thickness of the STN compensation film at this stage was measured
and was found to be 5.0 .mu.m. From the polarization transmission
spectrum profile of the STN compensation film, it was found that
the orientation (helical structure) of liquid crystal molecules was
twisted to the film thickness direction by 240.degree. and the
twist angle of the helix (rotation angle) was 240.degree..
Further, an STN compensation film having a twist angle in a reverse
direction to that of the above-mentioned film was prepared, and
these were laminated such that liquid crystal molecules would cross
at right angles at the joined parts, inserted between two
polarization plates having absorption axes crossing each other at
right angles, and observed visually to confirm excellent black
color. Therefore, it was confirmed that the film (STN compensation
film) formed as described above acted as an optical compensation
film for an STN element.
Example 5
Prevention of Occurrence of Reverse Twist Domain for TN Element
On an ITO film of a glass substrate equipped with an ITO film, a
polyimide orientation film (LX-1400, manufactured by Hitachi
Chemical Dupont) application solution was applied by a spin coater,
dried for 5 minutes in an oven at 100.degree. C., and then baked
for 1 hour in an oven at 250.degree. C. to form an orientation
film. Further, the surface of the film was subjected to orientation
treatment by performing rubbing treatment such that a rubbing angle
was 90.degree., to produce two glass substrates equipped with
orientation films.
The glass substrates were placed so that the orientation films
faced each other, and pasted by a two-part epoxy resin adhesive
into which spacer beads having a diameter of 6 .mu.m had been
mixed, to form a cell for driving. The thickness of this cell was
measured by a light interference method and was found to be 5.4
.mu.m.
Into the above-mentioned cell, the following composition was
poured. The following light-reaction type chiral agent of the
present invention (exemplified compound (2)) was synthesized by the
above-mentioned synthesis method.
[Composition] Nematic liquid crystal composition (ZLI-1132,
manufactured by Merck) 99.9% Light-reaction type chiral agent of
the present invention (exemplified compound (2) described
previously) 0.1%
After the pouring, the cell for driving was inserted between two
polarization plates whose absorption axes crossed at right angle,
and observed visually, to find no occurrence of reverse twist
domain. Therefore, there was no reduction in contrast by occurrence
of reverse twist, and images excellent in contrast and color
purities would be expected to be displayed.
Example 6
Measurement of Change of Helical Pitch by Light Irradiation
2 parts of a light-reaction type chiral agent of the present
invention (exemplified compound (14)) synthesized by the
above-mentioned synthesis method (Synthesis of light-reaction type
chiral agent (14)) and 98 parts of a nematic liquid crystal
composition (ZLI-1132, manufactured by Merck) were mixed, and
poured into a wedge type cell (glass thickness 1.1 mm, blue plate)
on which uni-axial orientation treatment had been performed by a
polyimide orientation film. Here, helical pitch at room temperature
was measured using a polarization microscope and was found to be
1.14 .mu.m. This was calculated in terms of helical twisting power
(HTP) to give a value of 44 .mu.m.sup.-1.
Next, the above-mentioned wedge type cell was irradiated with
ultraviolet radiation for 3 minutes at an irradiation strength of
300 mW/cm.sup.2 from a high pressure mercury lamp. After
irradiation, helical pitch at room temperature was measured in the
same manner as described above to find a pitch changed to 3.6
.mu.m. This was calculated in terms of HTP to give a value of 14
.mu.m. Therefore, the change rate of HTP was 3.14.
As described above, the twisting power of helix (HTP) could be
significantly changed by irradiation with ultraviolet radiation.
Further, the twist direction before and after irradiation with
ultraviolet radiation was confirmed by a contact method and was
found to be right-twisting both before and after irradiation.
Example 7
Production of Wide Band Circular Polarization Reflection Plate
(1) Preparation of Substrate
On a glass substrate, a polyimide orientation film (LX-1400,
manufactured by Hitachi Chemical Dupont) application solution was
applied by a spin coater, dried for 5 minutes in an oven at
100.degree. C., and then baked for 1 hour in an oven at 250.degree.
C. to form an orientation film. Further, the surface of the film
was subjected to orientation treatment by rubbing treatment to
produce a glass substrate equipped with an orientation film.
(2) Production
On the orientation film of the glass substrate equipped with the
orientation film obtained above, an application solution prepared
by the following recipe was applied by a bar coater, and kept for 5
minutes on a hot plate of 110.degree. C., and then irradiated with
light by an ultrahigh pressure mercury lamp via a band pass filter
having a light source central wavelength at 365 nm for 5 minutes,
at the same temperature. The following light-reaction type chiral
agent of the present invention (exemplified compound (15)) was
synthesized by a method analogous to the above-mentioned synthesis
method.
Next, the plate was kept in a dark place for 5 minutes while being
maintained at 110.degree. C. Then, the band pass filter was
removed, and the whole surface was irradiated with light by the
same ultrahigh pressure mercury lamp as described above at an
irradiation energy of 500 mJ/cm.sup.2, while spraying a nitrogen
gas, to give hardening by polymerization. As described above, a
circular polarization reflection plate was produced.
[Recipe of application solution] ##STR30## 42 parts by weight
##STR31## 42 parts by weight ##STR32## 8 parts by weight
Exemplified compound (15): light-reaction type chiral agent
##STR33## 4 parts by weight ##STR34## 2 parts by weight ##STR35## 5
parts by weight Chloroform 400 parts by weight
The circular polarization reflection plate obtained above
manifested selective reflections in a wide wavelength range ranging
from 450 nm to 630 nm, that is, had a band property sufficient for
a wide-band circular polarization reflection plate. Further, right
circular polarization reflectance at a selective reflection
wavelength of 550 nm was 98%.
Example 8
Production of Liquid Crystal Color Filter
(1) Preparation of Filter Substrate
On a glass substrate, a polyimide orientation film (LX-1400,
manufactured by Hitachi Chemical Dupont) application solution was
applied by a spin coater, dried for 5 minutes in an oven at
100.degree. C., and then baked for 1 hour in an oven at 250.degree.
C. to form an orientation film. Further, the surface of the film
was subjected to orientation treatment by rubbing treatment to
produce a glass substrate equipped with an orientation film.
(2) Production of Filter Layer
On the orientation film of the glass substrate equipped with the
orientation film obtained above, an application solution for a
photosensitive resin layer prepared by the following recipe was
applied by a spin coater, and dried for 2 minutes in an oven at
110.degree. C., to form a photosensitive resin layer. The following
light-reaction type chiral agent of the present invention
(exemplified compound (14)) was synthesized by the above-mentioned
synthesis method.
[Recipe of application solution for photosensitive resin layer]
##STR36## 42 parts by weight ##STR37## 42 parts by weight ##STR38##
8 parts by weight Exemplified compound (14): light-reaction type
chiral agent ##STR39## 3 parts by weight ##STR40## 2 parts by
weight Dipentaerythritol hexaacrylate 3 parts by weight Chloroform
400 parts by weight
Next, the plate was kept for 5 minutes on a hot plate of
110.degree. C. so as to give contact at the surface of the glass
substrate, to cause color development of the photosensitive resin
layer. Further, on this photosensitive resin layer, an ultrahigh
pressure mercury lamp was placed via a photomask carrying regions
having different transmittances at three grades (0%, 46%, 92%) and
being arranged corresponding to blue picture elements, green
picture elements and red color elements, and a band pass filter
having a central wavelength of 365 nm. The resin layer was
irradiated with light by the ultrahigh pressure mercury lamp though
the photomask and band pass filter, to realize patterning. At this
stage, the irradiation energy was 300 mJ/cm.sup.2 for red picture
elements and the irradiation strength was 30 mW/cm.sup.2.
Next, the photomask and band pass filter were removed, and the
layer was irradiated on the whole surface with light by the same
ultrahigh pressure mercury lamp as described above at an
irradiation energy of 500 mJ/cm.sup.2, while spraying a nitrogen
gas, to give hardening by polymerization. Further, for promoting
the degree of hardening of the filter part (photosensitive resin
layer), the layer was baked for 20 minutes in an oven at
220.degree. C., to obtain a color filter having patterns of red
picture elements, green picture elements and blue picture elements
formed therein.
In the above-mentioned patterning, the helical pitch of a liquid
crystal (twisting power of liquid crystal) could be significantly
changed by irradiation and picture element patterns of a red color,
green color and blue color having high color purities could be
formed.
Example 9
Production of Optical Compensation Film for STN Element
On triacetylcellulose (TAC) having a thickness of 80 .mu.m, a
polyethylene vinyl alcohol (PVA) film having a saponification
degree of 99.5% was formed by a bar coat method, and heated at
110.degree. C. for 3 minutes. Rubbing treatment was performed on
this PVA film. Further, an application solution prepared by the
following recipe was applied on the PVA film by a bar coater while
heating, and this was dried in an oven at 120.degree. C. for 3
minutes, to form a film. The following light-reaction type chiral
agent of the present invention (exemplified compound (17)) was
synthesized by the above-mentioned synthesis method.
[Recipe of application solution] ##STR41## 42 parts by weight
##STR42## 42 parts by weight Exemplified compound (17):
light-reaction type chiral agent ##STR43## 0.3 parts by weight
##STR44## 3 parts by weight Chloroform 400 parts by weight
Next, the film was polymerized to be hardened by irradiation over
the film with ultraviolet radiation using an high pressure mercury
lamp (irradiation energy 1000 mJ/cm.sup.2) at 100.degree. C., to
produce an optical compensation film for an STN element
(hereinafter, referred to as "STN compensation film"). The film
thickness of the STN compensation film as this stage was measured
and was found to be 5.0 .mu.m. From the polarization transmission
spectrum profile of the STN compensation film, it was found that
the orientation (helical structure) of liquid crystal molecules was
twisted to the film thickness direction by 240.degree. and the
twist angle of the helix (rotation angle) was 240.degree..
Further, an STN compensation film having a twist angle of the
reverse direction to that of the above-mentioned film was prepared.
These were laminated such that liquid crystal molecules crossed at
right angle at the joined parts, were inserted between two
polarization plates having absorption axes crossing each other at
right angle, and observed visually to confirm excellent black
color. Therefore, it was confirmed that the film (STN compensation
film) formed as described above acted as an optical compensation
film for an STN element.
Example 10
Prevention of Occurrence of Reverse Twist Domain for a TN
Element
On an ITO film of a glass substrate equipped with the ITO film, a
polyimide orientation film (LX-1400, manufactured by Hitachi
Chemical Dupont) application solution was applied by a spin coater,
dried for 5 minutes in an oven at 100.degree. C., and then baked
for 1 hour in an oven at 250.degree. C. to form an orientation
film. Further, the surface of the film was subjected to orientation
treatment by performing rubbing treatment so that the rubbing angle
was 90.degree., to produce two glass substrates equipped with
orientation films.
The glass substrates were placed so that the orientation films
faced each other, and pasted by a two-part epoxy resin adhesive
into which spacer beads having a diameter of 6 .mu.m had been
mixed, to form a cell for driving. The thickness of this cell was
measured by a light interference method and was found to be 5.4
.mu.m.
Into the above-mentioned cell, the following composition was
poured. The following light-reaction type chiral agent of the
present invention (exemplified compound (14)) was synthesized by
the above-mentioned synthesis method.
[Composition] Nematic liquid crystal composition (ZLI-1132,
manufactured by Merck) 99.9% Light-reaction type chiral agent of
the present invention (exemplified compound (14) described
previously) 0.1%
After the pouring, the cell for driving was inserted between two
polarization plates whose absorption axes crossed at right angle,
and observed visually, to find no occurrence of reverse twist
domain. Therefore, there was no reduction in contrast by occurrence
of reverse twist, and images excellent in contrast and color
purities would be expected to be displayed.
* * * * *